Study On Asymmetric Involute Gear Transmission Characteristic And Its Application Foundation

Gear is one of the driving parts of power machinery and equipment. In order to improve the bending strength at the tooth root of gear, a kind of new gear,namely, asymmetric gear was put forward. The advantages of this kind of gear have larger carrying capacity, smaller volume, lighter weight and longer life. The study of asymmetric gear has important theoretical direction and realized significance to the application of the heavy load and high-speed gear for aerospace. The methods of theory analysis combined numerical simulation and experimental test are used in the paper. The asymmetric involute gear was used as object, the transmission performance of the single & double moduli asymmetric involute gear is researched under the friction force between teeth.The new technique, the new theory,and the new methods, of improving the transmission performance are explored. The main works are as follows:1. The generated principles of the tooth profile curved surface of asymmetric involute gear are stated, the parametric equation of single & double moduli asymmetric involute rack tools is deducedAccording to the structural features of asymmetric involute gear, the generated principles of the tooth profile curved surface of asymmetric involute gear are stated, this will establish the theory basis for popularizing the asymmetric involute gear. To accelerate the study and application of single & double moduli asymmetric involute gear, the parametric equation of single & double moduli asymmetric involute rack tools are deduced according to the characteristic of single & double moduli asymmetric involute gear.2. The mathematic models on tooth face contact stress and tooth root bending stress of asymmetric involute gear are established under friction force between teethThe mathematic models on tooth face contact stress and tooth root bending stress of asymmetric involute gear with double pressure angles are deduced by through fully analyzing the forces exerted on the driving gear of asymmetric spur gear drive under the action of sliding friction. Simulation results provide a theoretical basis to improve the tooth face contact strength and tooth root bending strength of asymmetric involute gear with double pressure angles.3. The mathematic models of gear supports of asymmetric gear driving system are established under the sliding friction forceThe author of the paper deduced the calculation equation of the gear supports reaction, under the action of the sliding friction between teeth, through fully analyzing the forces exerted on the driving gear of reducing-speed asymmetric spur gear drive system with double pressure angles in the single & double gears meshing range. And presented the index of gear supports reaction fluctuation in the condition of the random interteeth load.Simulation results provide the theoretical references for improving the transmission smoothness of the asymmetric gear with double pressure angles. 4. Establish the mathematical model of the sliding coefficient of asymmetric involute gear tooth profileThe vector calculation formula of tooth profile sliding coefficient of single & double moduli asymmetric involute gear was deduced by using the normal curvature of meshing point relative velocity direction and the common normal line vector of meshing point on the contac tooth profile under the spatial meshing state.And the simplified formula of tooth profile sliding coefficient of single & double moudli asymmetric involute spur gear was also deduced. Simulation results provide the theoretical references for revealing the working principle of friction and wear of the asymmetric gear with double pressure angles.5. Prediction of meshing efficiency on asymmetric gear with double pressure anglesThe author of the paper deduced the calculation equation of the gear mesh efficiency in the condition of the random interteeth load, under the action of the sliding friction between teeth, making use of the radii of teeth outline curvature at the mating points, through fully analyzing the forces exerted on the gears'teeth of single or double moduli asymmetric involute spur gear drive system with double pressure angles in the single & double gears meshing range.And, calculation of the mating efficiency was carried out by changing the sliding interteeth friction, pressure angle, modulus and gear's rotating speed ratio on the diving & driven gears of single or double moduli asymmetric spur gear drive system with double pressure angles. And provides a fast, convenient way in order to determine the transmission efficiency of asymmetric spur gear drive system with double pressure angles.6. Testing and experimental design of the asymmetric involute gear drive system with double pressure angles.The test platform of the asymmetric involute gear driving system with double pressure angles was designed, the noise and vibration acceleration of gear driving equipment was tested,and the dynamic performance of both unsymmetric gear and symmetric gear are analyzed under different meshing states in this paper.The results show that the effect of the sliding friction between teeth can not be neglected in the tooth root bending stress calculation and tooth face contact stress calculation of asymmetric involute gear with double pressure angles. The performance index of noise and vibration, meshing efficient, tooth profile sliding coefficient,and gear strength,of asymmetric involute gear are superior to symmetric involute gear. Compared to single modulus symmetrical involute gear,dual modulus asymmetric involute gear can not only save material, reduce weight, improve tooth surface contact strength and root bending strength, and because of the smaller sliding coefficient of tooth profile, tooth wear lighter. Compared with the symmetric involute gear, asymmetric involute gear tooth face contact stress can be reduced 28.86%, tooth root bending stress can be reduced 6.37%. Considering the tooth surface friction, asymmetric involute gear tooth surface contact stress will increase to 7.51%, the tooth root bending stress will increase to 7.12%.The tooth face contact stress of double moduli asymmetric involute gear can reduce to 34.74% comparing with single modulus symmetric involute gear. Tooth profile Sliding coefficient of tooth addendum can reduce to 17.42%, Sliding coefficient of tooth root can reduce to 40.28% by increasing the pressure angle for single modulus asymmetric involute gear. Tooth profile sliding coefficient of tooth addendum can reduce to 21.81%, Sliding coefficient of tooth root can reduce to 34.75% by increasing the pressure angle for double moduli asymmetric involute gear.The meshing efficiency of symmetric involute gear is 97.73%, but the meshing efficient of symmetric involute gear is 98.24% under the same conditions.The noise of symmetric involute gear is from 83.6 to 85.0 dB, but the noise of asymmetric involute gear is from 72.6 to 73.7 dB, The vibration acceleration peak-peak of symmetric involute gear is from 4.49 G to -4.29G, while on the asymmetric involute gear is from 1.02 G to -1.08 G. The results show that the asymmetric gear can significantly improve the transmission performance of the gear, has very important significance for the high-speed, overload, high-power gear working environment.The dissertation is supported by National Natural Science Foundation (No.51075192).